1. Field of the Invention
The present invention relates to a system and a method for monitoring and controlling semiconductor process, and more particularly to a real-time system for monitoring and controlling film uniformity and a method of applying the same.
2. Description of Related Art
With the advances in semiconductor industry, integrated circuits develop towards miniature and high performance. To meet the requirements for high integration and great performance, a multi-layer design is adopted. Owing to distinct film thickness and electrical characteristics of devices, each film functions in a different manner. Specifically, the surface profile of the film on a wafer poses great impact on subsequent processes, such as a chemical mechanical polishing (CMP) process, a photolithography and etching process, and so on. Thus, it is always a dominant concern for the industry to determine how to accurately measure the thickness and uniformity of the film.
In general, the method for measuring the thickness of the film includes interferometry, scattering measurement and reflectometry. U.S. Pat. No. 5,450,205 provides an apparatus for measuring the thickness as well as the change in the thickness and a method using the same. As the film is etched or deposited, a charge couple device (CCD) camera is utilized to perform interferometry so as to measure the thickness and etching/depositing uniformity of the film on the wafer through a viewport with a certain size.
However, the viewport on the reaction chamber is required in said method for adopting the CCD camera. Moreover, the CCD camera is easily interfered by noises resulting from light generated by plasma within the reaction chamber and collects few signals, leading to less variation in the signals and insufficient sensitivity. In consequence, the film profile cannot be accurately measured. In addition, a high-coherence point light source e.g. a laser beam is required in said conventional method performing interferometry. Nevertheless, since the wafer occupies a large area, the thickness of every portion of the wafer cannot be timely measured through the point light source in a short period of time, and the measurement at many points has to be performed simultaneously, which brings about high operation complexity.